Method for extracting noble and non-ferrous metals from refractory raw materials

ABSTRACT

A method for extracting noble and non-ferrous metals from refractory raw materials includes a first stage electric treatment of ground pulp in a chloride solution and a subsequent second stage of extracting commercial metals, carried out in one reactor using electrolysers with graphite anodes and steel cathodes. The reactor is fed with pulp having an S:L ratio of 1:(1-20) in a solution with a chlorine concentration of 60-180 g/L, being acidified to pH=0.2-1.0, it&#39;s agitated, the volume current density is set to 1000-10000 A/m 3  and the electrolyser&#39;s voltage to 2-5 V, then maintained constant. The first stage terminates by a transition of electric current through a maximum and chaning pH to 1-2. At the second stage, the cathode current density is set to 50-200 A/m 2 ., until pH reaches 3-7. Cathode deposits of both stages are combined and further processed by known methods.

CROSS-REFERENCE TO RELATED APPLICATION

This U.S. patent application claims priority under 35 U.S.C. 119 (a)through (d) from a Russian patent application RU2012134684 filed on 14Aug. 2012 hereby entirely incorporated by reference.

FIELD OF THE INVENTION

The invention relates to metallurgy of noble metals, namely, tohydrometallurgical methods for processing refractory gold-containing andsilver-containing concentrates and ores.

BACKGROUND OF THE INVENTION

Metal extraction from refractory gold-containing ores, where noblemetals are concentrated in sulphide minerals in the form of anisomorphic admixture or as a solid solution and are not accessible fordirect cyanidation is known to present substantial technicaldifficulties. Globally, the most widespread process involves multiplestages, including oxidizing roasting in an oven, cyanidation of theroasted product to produce gold-containing solutions, extraction of goldfrom these solutions using sorption, cementation or electrolysis. Arefractory ore hydrochlorination process is also known, which can solvethe problem of comprehensive extraction of valuable components due tothe high chemical activity of chlorine with respect to gold and loweractivity with respect to gangue components.

A version of the hydrochlorination process, called electrochlorination,involves direct electrochemical treatment of refractory ores usingchlorine, which is released during the electrolysis of solutions ofalkaline metal chlorides. Thus, patent (U.S. Pat. No. 351,576, Cassel,Oct. 26, 1886) describes a method of extracting gold from ores using anelectrochemical cell. The anode and cathode compartments of the latterare separated by a porous asbestos septum and, essentially, form adiaphragm electrolyser. The anode compartment generates chlorine, whichinteracts with ore under vigorous agitation, and the cathode separatesgold from the solution filtered by the septum. Invention (GB190920471(A), Cobb, Sep. 7, 1909) suggests that ore in the form of pulp withparticle size 60 mesh with added sodium chloride solution (5 g/L) betreated using electrolysis in an undivided electrolyser with leadelectrodes. Gold plates out on the cathode, while silver chloride isprecipitated and can be removed by electrolysis or using any other knownprocess. Invention (U.S. Pat. No. 3,957,603, Rhodes, May 18, 1976)describes a method of electrochlorination for extracting gold fromrefractory ores, which involves preparing pulp from ground gold ore withwater and sodium chloride in the first vessel and placing an anode inthe said first vessel. The cathode is placed in the second vesselequipped with a porous membrane to make electric current pass throughthe membrane. Chlorine generated at the anode interacts with pulp andmakes gold dissolve in the form of auric chloride.

Invention (WO8706274 (A1), Kelsall, Oct. 22, 1987) describes a methodand apparatus for extracting gold using chlorine and chloride solutionsfrom scrap material, ore or other material, where the oxidizer is alsoelectrochemically generated in the anode compartment of anelectrochemical cell. The oxidizer reacts with the said raw material andprovides the formation of soluble compounds, which are converted to goldin the cathode compartment of the cell.

There are descriptions of other methods of electrochemical chlorinationfor the oxidation of refractory gold ore and release of metals fromrefractory sulphide raw materials to the solution. To isolate the metalsthemselves either sorption or other well-known technologies notassociated with previous electrochlorination are recommended, forexample, electrolysis of gold from pulp. (See “Chloride metallurgy ofgold”, Zyryanov M. N., Leonov S. B., Moscow, “SP Internet Engineering”,1997, pp. 263-267). In these experiments, gold electrolysis from pulpwith a particle size of 0.15 mm was carried out on lead or graphiteelectrodes at a current density of 50-100A/m² with a degree ofextraction 98-99%.

Invention (EP0115500A, EVERETT, DEXTEC METALLURG, Aug. 15, 1984, theclosest analogue) describes a method of extracting silver and gold fromores and concentrates with the use of electrochlorination. The methodinvolves preparing a mixture of ore or concentrate (pulp 300 g/L) and astrong electrolyte—NaCl (250 g/L). The mixture is kept at theelectrolyte boiling temperature, at which silver and gold becomedissolved, the pH varies between 3.0 and 8.0. The redox potential ismaintained at 750-850 mV. The metal is produced at the cathode and canbe separated mechanically. This method also employs a diaphragmelectrolyser; chlorine is fed in the gaseous form or in a hypochlorite.The electrode system works only to precipitate the metals from thesolution. Complete precipitation at the cathode is not guaranteed, asthe diaphragm hinders the process.

At the same time electrochlorination in pulp and recovery of preciousmetals in a unified technological cycle using electrolysers of the sametype appears promising.

BRIEF SUMMARY OF THE INVENTION

This invention relates to an improvement of a method for extracting goldand other noble metals from refractory raw materials without preparatorysulphide oxidation operations, where both processes, i.e.electrochlorination and the preparation of high-quality precipitates ofgold and other valuable metals, are carried out in one reactorpractically simultaneously. Besides, the invention can be used for awide range of ores and materials, including natural sorbents, since atthe recommended process temperatures, sorption from the solutionsutilized is completely suppressed.

The inventive method for extracting noble and non-ferrous metals fromrefractory raw materials includes the stage of electric treatment ofground raw material pulp in a chloride solution and the subsequent stageof isolation of commercial metals, where both stages are carried out inone reactor using at least one undivided electrolyser. The material fedto the electric treatment stage is ground raw material pulp with the S:Lratio of 1:(1-20) in a chloride solution with the chlorine concentrationof 60-180 g/L, which is acidified to the pH of 0.2-1.0. At the beginningof the electric treatment stage under pulp agitation, the volumeelectric current density is set at 1000-10 000 A/m³ at the electrolyservoltage of 2-5 V, which is maintained constant. The end of the pulpelectric treatment process is determined by the transition of thecurrent vs. time curve through a maximum and subsequent pH change to1-2. The processed pulp is fed to the commercial material extractionstage; for this, cathode current density in the electrolyser is set inthe range of 50-200 A/m². The extraction stage is considered completewhen pH reaches 3-7. After this the cathode deposits of both stages arecombined and sent for extracting commercial metals using known methods.

Refractory raw material is an ore, gravity concentrate or flotationconcentrate of pyrite or arsenopyrite ores with the sulphide content of20-80% by weight. The particle size of the ground raw material shall notexceed 0.15 mm.

The reactor may contain segregate electrolysers for the pulp electrictreatment stage and commercial product extraction stage equipped withfacilities for agitating the pulp and removable cathodes. The reactormay contain an electrolyser with a selector to switch between the pulpelectric treatment modes. The chloride solution can be selected from thegroup of chloride solutions containing the chlorides NaCl, KCl, CaCl₂and MgCl₂. The electric treatment stage is carried out at temperaturesabove 60° C., predominantly in the range 60-90° C., and the commercialmethod extraction stage is carried out at temperatures in the range20-50° C. Cathode deposits can be separated from cathodes mechanically.In an undivided electrolyser steel cathodes and anodes made of graphiteor of a material based on ruthenium oxide and titanium can be used.

The technical result is the possibility to concurrent extraction ofcommercial metals in the process of ore material electrochlorinationwith subsequent additional recovery of the desired materials at the samecathodes of the reactor based on undivided electrolysers of the sametype.

BRIEF DESCRIPTION OF THE DRAWINGS

The inventive method is illustrated in the drawings, wherein:

FIG. 1 shows a flow chart of the inventive method;

FIG. 2 shows a waveform for dependence of current volume density I(A/m³) and pH upon time in an electrolyser at an electric treatmentstage of the inventive method;

FIG. 3 shows a waveform for dependence of cathode current density I,(A/m²) and pH upon time at an extraction stage of the inventive method.

DETAIL DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

While the invention may be susceptible to embodiment in different forms,there are described in detail herein below, specific embodiments of thepresent invention, with the understanding that the instant disclosure isto be considered an exemplification of the principles of the invention,and is not intended to limit the invention to that as described herein.

The inventive method involves carrying out two stages of refractorymaterial pulp treatment with a direct electric current in an undividedelectrolyser with various treatment modes and reaction conditions.

A first stage of the inventive method is intended to oxidise sulphidesas completely and quickly as possible. This is favoured by vigorousagitation, acidic medium, heating and high current values. Gold isliberated and passes into the solution under the action of chlorine asan oxidiser and chloride ion as a complexing agent.

In this process, electric current acts as a reagent, a source ofchlorine. It must be passed in the amount sufficient for oxidisingsulphides. Therefore, each type of raw material will have an individualspecific electric power consumption, which is determined by sulphidecontent. But arbitrary electric power cannot be supplied. If the poweris too low, the process will be unnecessarily protracted. If the poweris too high, excess unreacted chlorine will escape into the gas phaseand become useless. This means that there is an optimum value, whichmust be relative to the volume (V) of the reaction mass, i.e., expressedin A/m³, which is done in the claimed invention.

The rate of the chemical oxidation reaction can be increased by heatingthe reaction mass and by creating an acidic medium, where the oxidativepotential of chlorine increases. We have established the range wherefurther decrease in pH values below 0.2 does not increase the initialrate of the reaction, whereas pH increase above 1.0 decreases it.

As for the first stage temperature, higher temperature, whilesignificantly reducing the overall process time, generally does notaffect the end results of the subsequent gold recovery stage, and itsoptimum value must be determined on the basis of economicconsiderations. However, a very important point must be taken intoaccount when selecting the temperature. If the source material containschemically stable natural sorbents (coal, shungite, graphite), which arenot degraded by the process, the temperature must be kept at or above60° C., which allows to completely suppress secondary sorption of goldby these sorbents and avoid additional losses.

Pulp dilution. Undoubtedly, higher pulp dilution to S:L(ton:m³)=1:(1-20) reduces the overall process time, since there is lesssolid material, while the volume electric current density per unitvolume of the reaction mass remains unchanged; however, this does notlead to a noticeable increase in gold recovery factor nor to a reductionin specific electric power consumption. Thus, the optimum parametersshould be selected based on economic considerations.

Reagent concentration (60-180 g/L in terms of the chloride ion). Theupper limit is selected based on the reasoning that above it lies therange of saturated solutions, in which the solubility of gases isseverely reduced. Given the fact that the process involves chlorine inthe atomic and molecular form, reduction of its solubility begins tohamper the process. The lower limit is based on the fact that furtherreduction decreases gold recovery while having no effect on thecompleteness on sulphide oxidation.

A second stage of the inventive method is recovery of commercial metals.At this stage, once sulphides are almost completely oxidised, generatinglarge amounts of chlorine is not required. It is only necessary tomaintain a working concentration, which will allow to complete theprocess of gold dissolution and will not interfere with gold depositionon the cathodes. Pulp temperature is not crucial, since gold dissolutionoccurs at a rather high rate even at room temperature. However, ifnatural sorbents are present, the temperature at this stage must also bemaintained at or above 60° C. The transition of electric current loadthrough a maximum I_(max) indicates that the majority of sulphides havebeen oxidised, and pH increase to 1-2 (pH₁) marks the point of completetermination of the process, because at this point acidic reactionproducts cease to form.

Then the electric current load I_(c) must be set to bring cathodecurrent density to 50-200 A/m². In pH₁ range iron salts begin tohydrolyse and yield hydrate precipitates. At this point gold must berecovered as completely as possible to avoid its capture by the formingprecipitate. This is achieved by significantly reducing current load andslowing the pulp neutralisation process, which prevents the precipitatefrom forming. Reduction processes at the cathode are carried out untilpH reaches 3-7 (pH₂). At this point precipitation of gold with otherelements at the cathode is brought to a completion, whereas iron andarsenic are almost completely precipitated. The metal is deposited on acathode in the form of a tight precipitate. As it accumulates, thecathode is removed and replaced with a new one, while the deposit isremoved either mechanically or chemically. Then the gold-containingdeposit is processed using known methods to produce metalic gold. Afterthe extraction process is complete, the pulp is filtered, the solidresidue is washed and sent to a tailings storage facility, and thesolution obtained is corrected and sent to the process input for reuse.

FIG. 1 shows the method flow chart. The refractory raw material (ore,flotation concentrate, gravity concentrate) is fed to the grinding stage(if necessary). Then the raw material with particle size not more than0.15 mm is sent to the pulp preparation stage. Pulp is prepared with theS:L ratio (ton:m³) of 1:1-20 in a chloride solution with the chlorineconcentration of 60-180 g/L. Chlorides of alkaline metals NaCl, KCl,CaCl₂, MgCl₂ and mixtures thereof are used as chlorides. Pulp isacidified to the pH of 0.2-1.0; hydrochloric acid can be used as anacidity regulator.

The pulp thus prepared is added to a reactor, which constitutes one ormore undivided electrolysers having means for regulating the electriccurrent and means for controlling pulp acidity and temperature. Thereactor is equipped with means for vigorously agitating the pulp in theprocess of electric treatment. At the beginning of the electrictreatment stage under pulp agitation, the volume electric currentdensity is set at 1000-10 000 A/m³ at the electrolyser voltage of 2-5 V,which is maintained constant. As electric current is passed through thesolution of sodium chloride or other chlorides, the electrochemicalprocess results in the liberation of chlorine, which, acting as a strongoxidiser, breaks down sulphide minerals and dissolves their component,including the commercial metals present in the sulphides. The process ofpulp electric treatment is accompanied with commercial metal depositionon metallic electrodes (cathodes). The termination of the pulp electrictreatment process is determined using two signs: the transition of thecurrent vs. time curve through a maximum (I_(max)) and subsequent pHchange to 1-2.

Then additional extraction of the commercial material is performed. Forthis, cathode current density I_(c) in the electrolyser is set in therange of 50-200 A/m² (see FIG. 3). The extraction stage is consideredcomplete when pH reaches 3-7 (pH₂). After this the cathode deposits ofboth stages are combined and sent for extracting commercial metals usingknown methods (see FIG. 3).

The reactor can be implemented in the form of a plurality of separatelycontrolled electrolysers for the pulp electric treatment stage andcommercial product extraction stage, equipped with facilities foragitating the pulp and removable cathodes, or as a single electrolyserwith a selector to switch between the pulp electric treatment mode andthe commercial product extraction mode. As the commercial metal depositsare accumulated, the cathodes are removed from the reactor at regularintervals. The deposits are separated mechanically or chemically. Thecleaned cathodes are reused. The undivided electrolyser can have steelcathodes and anodes made of graphite or of a material based on rutheniumoxide and titanium oxide. Such electrodes are known to be used in thechlorine industry and enable to considerably reduce electric powerconsumption for electrolysis.

Carrying out the process in solution ensures the absence of gaseousemissions, while the small amounts of chlorine released from thesolution can be removed by a ventilation system and returned into theprocess. Solid waste that is sent to the tailings storage facilitycontains harmful substances in poorly soluble form. In particular,arsenic is present as iron arsenate, which is similar to the naturalmineral scorodite.

The achievement of the technical result was demonstrated in thefollowing laboratory experiments in gold and silver recovery fromflotation and gravity concentrates using undivided electrolyserprototypes; the numerical values of current density and pH for eachexperiment are given in the Table.

Experiment 1

The process was performed in a glass vessel with the capacity of 0.8dm³. Agitation was performed using a magnetic stirrer with a hot top.Reduction in pulp volume was compensated by adding distilled water.

The electrode cell consisted of two graphite anodes and one replaceablecathode of stainless steel on a nonconductive suspension installedbetween the anodes, 20 mm away. The electrodes were rectangular and hadthe dimensions of 55×120 (mm). The cell was immersed into the pulp 80-90mm deep. The cell was powered by a DC power supply, which couldstabilise the electric current or the voltage. As the depositaccumulated, the cathode was replaced with a new one, and the removedcathode was washed, dried, and the deposit was removed mechanicallyusing a scraper.

Raw material and preparation thereof. The refractory raw materialsubject to processing is a flotation concentrate with particle size of0.15 mm containing pyrite 58.8%, arsenopyrite 22.2%, gold 15.1 g/t, andsilver 95.0 g/t. 0.5 dm³ of a sodium chloride solution with the chlorideion concentration of 120 g/L was added to 100 g of the raw material. Thepulp was acidified with hydrochloric acid to pH 0.70 and heated to 75°C. under agitation.

Electric treatment stage. The electrode cell was immersed into the pulpand energised; stabilised voltage was set at 2.5 V. The total pulpvolume was 0.53 dm³, the cathode working area was 0.9 dm². Under theseconditions the electric treatment was carried out for 168 hours. Thecurrent volume density at the start of the experiment was set at 7000A/m³ and then increased to 9800 A/m²; in 168 h it decreased to 6200A/m³. During the process, pH dropped to 0.28 and then grew to 1.32.

Metal extraction stage. After 168 hours heating was turned off, and thecell was powered with 1.8 A current in the current stabilisation mode.The resulting electric current volume density of 3600 A/m³ correspondsto the cathode current density of 200 A/m², which is recommended forthis stage. The experiment proceeded in this mode for another 20 hours.During this time, pH increased to 6.11, and the metal extraction stagewas considered complete.

At the end of the experiment the processed pulp was filtered, the solidresidue (tailings) was washed, dried and weighed. The tailings mass was82.4 g, gold content was 0.78 g/t, silver content was 0.4 g/t. The massof the cathode deposits collected was 23.5 g. The content of gold is61.4 g/t, the content of silver is 344 g/t. Solution analysis showedgold concentration to be 0.01 mg/L, and silver concentration, 1.37 mg/L.Thus, gold was distributed across the products as follows: cathodedeposits: 95.5%; tailings: 4.2%; solution: 0.3%. Silver: cathodedeposits: 92.5%; tailings: 0.3%; solution: 7.2%.

Experiment 2

The process was performed in a glass vessel with the capacity of 1.2dm³. Agitation was performed using a magnetic stirrer. The electrodecell design and power supply are similar to those in Experiment 1. Thecell was immersed into the pulp 80-90 mm deep.

Raw material and preparation thereof. The refractory raw materialsubject to processing is a gravity concentrate with particle size of0.15 mm containing pyrite 39.9%, arsenopyrite 17,4%, and gold 50.1 g/t.0.8 dm³ of a sodium chloride solution with the chloride ionconcentration of 120 g/L was added to 100 g of the raw material. Thepulp was acidified with hydrochloric acid to pH 0.43 under agitation.

Electric treatment stage. The electrode cell was immersed into the pulpand energised; stabilised voltage was set at 2.5 V. The pulp was notheated; during the experiment, the temperature varied in the range of20-27° C. The total pulp volume was 0.83 dm³, the cathode working areawas 0.9 dm². The experiment proceeded under these conditions for 72hours. The current volume density at the start of the experiment was setat 1125 A/m³ and then increased to 5000 A/m²; in 72 h it decreased to4500 A/m³. During the process, pH dropped from 0.43 to 0.02 and thengrew to 1.82.

Metal extraction stage. Cathode current density was set constant at 70A/m². Electrolysis was carried out in this mode for another 21 hours.During this time, pH increased to 6.14, whereupon the metal extractionstage was considered complete.

At the end of the experiment the processed pulp was filtered, the solidresidue (tailings) was washed, dried and weighed. Tailings weight was48.3 g. Gold content was 4.4 g/t. The weight of the cathode depositscollected was 33.9 g. Gold content was 104.8 g/t. Solution analysisshowed gold concentration to be 0.02 mg/L. Additional analysis ofgraphite electrodes demonstrated them to contain 8.7 g/t of sorbed gold.

Thus, gold was distributed across the products as follows: cathodedeposits: 69.7%; sorbed on anodes: 25.6%; tailings: 4.2%; solution:0.5%.

Experiment 3

The process was performed in a glass vessel with the capacity of 10 dm³.Agitation was performed using a mechanical stirrer made of rigid PVCplastic.

Electrolysis was carried out using two electrode cells. Each of them wasmade of two rectangular graphite anodes with the dimensions of 140×200mm and one rectangular cathode of stainless steel with the dimensions of140×200 mm. The distance between the electrodes was 20 mm. The cellswere immersed into the pulp 115 mm deep. The cell was powered by a DCpower supply similar to that used in Experiments 1 and 2.

Raw material and preparation thereof. The refractory raw materialsubject to processing is a flotation concentrate with particle size of0.15 mm containing pyrite 10.9%, arsenopyrite 9.1%, and gold 12.8 g/t.6.0 dm³ of a sodium chloride solution with the chloride ionconcentration of 120 g/L was added to 1000 g of the raw material.Treatment was carried out under agitation at the temperature of 25-30°C. Pulp was acidified with hydrochloric acid to pH 0.68.

Electric treatment stage. The electrode cells were energised; stabilisedvoltage was set at 2.5 V. The total pulp volume was 6.3 dm³, the cathodeworking area was 6.4 dm². The experiment proceeded under theseconditions for 58 hours. The current volume density at the start of theexperiment was set at 1050 A/m³ and then increased to 2500 A/m²; in 58 hit decreased to 1700 A/m³. During the process, pH dropped from 0.68 to0.45 and then grew to 1.88.

Metal extraction stage. The process was continued in the currentstabilisation mode, the cathode current density was set at 65 A/m² (thevolume current density was 690 A/m³). The metal extraction stagecontinued for another 38 hours. During this time, pH increased from 1.88to 6.45, whereupon the metal extraction stage was considered complete.

At the end of the experiment the processed pulp was filtered, the solidresidue (tailings) was washed, dried and weighed. Tailings weight was848.4 g. Gold content was 0.11 g/t. The weight of the cathode depositscollected was 77.1 g. Gold content was 95.9 g/t. Solution analysisshowed gold concentration to be 0.28 mg/L. Additional analysis ofgraphite electrodes demonstrated them to contain 0.45 g/t of gold.

Thus, gold was distributed across the products as follows: cathodedeposits: 68.4%; sorbed on anodes: 15.1%; tailings: 0.9%; solution:15.6%.

Experiment 4

The process was performed in a glass vessel with the capacity of 0.8dm³. Agitation was performed using a magnetic stirrer. The electrodecell was analogous to that used in experiment 1, but the graphite anodeswere replaced with oxide ruthenium-titanium anodes of the same size, andsteel cathodes were used.

Raw material and preparation thereof. The same concentrate as inexperiment 3 was used. A solution of sodium chloride (0.5 dm³) with theconcentration of 120 g/L by the chloride ions was added to 100 g of theraw material. The pulp was acidified with hydrochloric acid to pH 0.58.

Electric treatment stage. The electrode cell was immersed into the pulpand energised; stabilised voltage was set at 3.0 V. The total pulpvolume was 0.53 dm³, the cathode working area was 0.9 dm². Theexperiment proceeded under these conditions for 24 hours. The currentvolume density at the start of the experiment was set at 6000 A/m³ andthen increased to 9100 A/m³; in 24 h it decreased to 3400 A/m³. Duringthe process, pH dropped from 0.58 to 0.46 and then increased to 1.62.

Metal extraction stage. After 24 h voltage was set constant at 2.5 B.Electrolysis was carried out in this mode for another 18 hours. Cathodecurrent density was set constant at 106 A/m². During this time, pHincreased from 1.62 to 5.84, whereupon the metal extraction stage wasconsidered complete.

At the end of the experiment the processed pulp was filtered, the solidresidue (tailings) was washed, dried and weighed. Tailings weight was83.6 g. Gold content was 0.66 g/t. The weight of the cathode depositscollected was 10.3 r. Gold content was 98.5 g/t. Solution analysisshowed gold concentration to be 0.26 mg/L.

Thus, gold was distributed across the products as follows: cathodedeposits: 84.6%; tailings: 4.6%; solution: 10.8%.

It is noteworthy that the results obtained in case of graphite anodesand oxide ruthenium-titanium anodes substantially did not differ.However, in case of using oxide ruthenium-titanium anodes energyconsumption per unit of feedstock was reduced. Besides, gold sorption onthe anodes did not occur, in contrast to the case of using graphiteanodes.

The described experiments demonstrate that a number of technologicalproblems can be solved in the course of pulp electrolysis: sulfides canbe oxidised in an environmentally safe way, the gold contained thereincan be dissolved, gold can be extracted directly from the pulp withoutfiltering and concentration using sorbents, and a product suitable fordirectly recovering metallic gold can be obtained at the cathodes.

The method can be implemented using equipment for grinding raw materialsand preparing solutions and pulp that is known in hydrometallurgytechnology, electrolysers of known designs, as well as means forcontrolling and adjusting the key process parameters.

TABLE METHOD IMPLEMENTATION MODES FOR THE DESCRIBED EXPERIMENTSExperiment 1 Experiment 2 Experiment 3 Experiment 4 Pulp volume Pulpvolume Pulp volume Pulp volume 0.53 dm³ 0.83 dm³ 6.3 dm³ 0.53 dm³Cathode area Cathode area Cathode area Cathode area 0.9 dm² 0.9 dm² 6.4dm² 0.9 dm² Electric Electric Electric Electric Time, current, Time,current, Time, current, Time, current, h A/m³ pH h A/m³ pH h A/m³ pH hA/M³ pH 1 7000 0.70 1 1125 0.43 1 1050 0.68 1 6000 0.58 6 8400 0.28 54125 0.32 22 2500 0.45 4 9100 0.46 19 9000 0.64 25 5000 0.02 48 23000.56 8 7920 0.52 29 9800 0.69 48 5000 0.30 58 1700 1.88 12 7550 0.61 519000 0.60 72 4500 1.82 59 690 1.88 18 3770 0.69 71 9000 0.50 73 790 1.8272 690 4.11 24 3400 1.62 84 9000 0.50 93 790 3.30 96 690 6.45 25 18001.62 116 8800 0.75 116 790 6.14 31 1800 2.08 142 6600 0.98 42 1800 5.84168 6200 1.32 169 3600 1.32 178 3600 2.16 188 3600 6.11

What is claimed is:
 1. A method for extracting noble and non-ferrousmetals from refractory raw materials containing the noble andnon-ferrous metals, said method comprising the steps of: providing areactor including at least one electrolyser having two electrodes: acathode and an anode; providing said refractory raw materials in theform of a ground raw pulp in a chloride solution characterized with a pHparameter and an S:L ratio of (1):(1-20) with a chlorine concentrationof 60-180 g/L being acidified such that the pH parameter ranges from 0.2to 1.0; feeding said ground raw pulp into the reactor; providing a stageof electric treatment of said ground raw pulp in said reactor, wherein:said ground raw pulp is subjected to agitation and to passing electriccurrent therethrough, wherein a volume current density of said electriccurrent is initially set at 1,000-10,000 A/m³ and further measuredduring the stage of electric treatment, and a voltage on the electrodesis set to 2-5 V and is maintained constant; the pH parameter of saidground raw material pulp is measured during the stage of electrictreatment; the stage of electric treatment is terminated at a time oftransition of the electric current through a maximum thereof and asubsequent change of the pH parameter to 1-2; the stage of electrictreatment results in obtaining a processed pulp and in formation offirst cathode deposites on the cathode; and providing an extractionstage for extracting said noble and non-ferrous metals from theprocessed pulp, wherein: the processed pulp is fed into said reactor; acathode current density of said electric current is set in the range of50-200 A/m², and further measured during the extraction stage; the pHparameter of said processed pulp is measured during the extractionstage; the extraction stage is completed when the pH parameter reaches3-7, wherein the extraction stage is characterized with a formation ofsecond cathode deposites on the cathode; and combining the first cathodedeposites and the second cathode deposites for further processing. 2.The method according to claim 1, wherein the refractory raw materialsare represented by an ore and/or gravity concentrate and/or flotationconcentrate of pyrite and/or arsenopyrite ores with the sulphide contentof 20-80% by weight.
 3. The method according to claim 1, wherein therefractory raw materials consist of particles characterized with aparticle size not exceeding 0.15 mm.
 4. The method according to claim 1,wherein said at least one electrolyser is equipped with facilities foragitating the pulp; and said at least one electrolyser is represented byeither a single electrolyser, or a plurality of separately controlledelectrolysers.
 5. The method according to claim 1, wherein the cathodeis made of metal and being removable, and the anode is made of graphiteor a material based on oxides of ruthenium and titanium.
 6. The methodaccording to claim 1, wherein the chloride solution contains one of thefollowing chlorides: NaCl, or KCl, or CaCl₂, or MgCl₂.
 7. The methodaccording to claim 1, wherein said ground raw pulp is acidified withhydrochloric acid.
 8. The method according to claim 1, wherein theelectric treatment stage is carried out at temperatures above 60° C.,and the extraction stage is carried out at temperatures in the range of20-50° C.
 9. The method according to claim 8, wherein the electrictreatment stage is carried out at temperatures in the range of 60-90° C.10. The method according to claim 1, wherein said refractory rawmaterials contain natural sorbents, and both the electric treatmentstage and the extraction stage are carried out at temperatures above 60°C.
 11. The method according to claim 10, wherein both the electrictreatment stage and the extraction stage are carried out at temperaturesin the range of 60-90° C.
 12. The method according to claim 1, whereinsaid first and second cathode deposits are separated from the cathodemechanically or chemically.
 13. The method according to claim 1, whereinsaid at least one electrolyser is controlled by a selector capable ofswitching between the electric treatment stage and the extraction stage.